The thickening of aqueous phases is generally carried out by incorporating therein hydrophilic polymers of all sorts, whether they are synthetic or of natural origin.
Among the polymers of natural origin, xanthan or guar gums are fairly widely used. They however have the conventional disadvantages of natural products, namely a fluctuating quality and price.
Among the hydrophilic synthetic thickeners most widely used are polymers in the form of self-reversible invert latexes or powders. They are used in a wide pH range and are often well tolerated by humans. Such compositions are described for example in French patents and patent applications published under the numbers 2721511, 2773805, 2774688, 2774996, 2782086, 2785801, 2786493, 2787457, 2789395, 2794034, 2794124, 2808446, 2808447 and 2810883.
These polymers are anionic and are essentially intended to thicken and/or emulsify cosmetic, dermo-pharmaceutical or pharmaceutical topical formulations which contain numerous constituents such as oils, nonionic or anionic surfactants, inorganic salts and/or weak acids.
Some formulations, in particular those intended for hair care, also contain cationic surfactants and/or cationic conditioning polymers. In this particular case, thickeners consisting of anionic polymers are not recommended because of electrostatic interactions between the positive and negative charges which cause precipitation of the polymer, and cationic thickening polymers such as those described in American patents published under the numbers U.S. Pat. No. 4,806,345 and U.S. Pat. No. 5,100,660 are preferably used.
Although the latter behave satisfactorily in an acidic medium and are compatible with cationic surfactants, they nevertheless lose their thickening power in formulations high in electrolytes.
Accordingly, the applicant focussed on developing novel thickeners of a cationic nature, which are compatible with cationic surfactants while preserving their thickening power in media high in electrolytes.